Method of Assembling a Drill Bit with a Jack Element

ABSTRACT

A method of assembling a drill bit with a bit body intermediate a shank and a working face with a plurality of blades comprised of at least one cutting element. The working face also comprising a jack element disposed within a pocket that may be substantially coaxial with the axis of rotation of the drill bit. The jack element may comprise an abrasion resistant material comprised of a material selected from the following including natural diamond, polycrystalline diamond, boron nitride, tungsten carbide or combinations thereof The jack element may be press fit within a pocket that is brazed within a receptacle of the drill bit such that it is substantially centered coaxial to the rotation of the drill bit.

BACKGROUND OF THE INVENTION

This invention relates to drill bits, specifically drill bit assemblies for use in oil, gas and geothermal drilling. Drill bits are continuously exposed to harsh conditions during drilling operations in the earth's surface. Bit whirl in hard formations for example may result in damage to the drill bit and reduce penetration rates. Further loading too much weight on the drill bit when drilling through a hard formation may exceed the bit's capabilities and also result in damage. Too often unexpected hard formations are encountered suddenly and damage to the drill bit occurs before the weight on the drill bit may be adjusted. When a bit fails it reduces productivity resulting in diminished returns to a point where it may become uneconomical to continue drilling. The cost of the bit is not considered so much as the associated down time required to maintain or replace a worn or expired bit. To replace a bit requires removal of the drill string from the bore in order to service the bit which translates into significant economic losses until drilling can be resumed.

The prior art has addressed bit whirl and weight on bit issues. Such issues have been addressed in the U.S. Pat. No. 6,443,249 to Beuershausen, which is herein incorporated by reference for all that it contains. The '249 patent discloses a PDC-equipped rotary drag bit especially suitable for directional drilling. Cutter chamfer size and backrake angle, as well as cutter backrake, may be varied along the bit profile between the center of the bit and the gage to provide a less aggressive center and more aggressive outer region on the bit face, to enhance stability while maintaining side cutting capability, as well as providing a high rate of penetration under relatively high weight on bit.

U.S. Pat. No. 6,298,930 to Sinor which is herein incorporated by reference for all that it contains, discloses a rotary drag bit including exterior features to control the depth of cut by cutters mounted thereon, so as to control the volume of formation material cut per bit rotation as well as the torque experienced by the bit and an associated bottomhole assembly. The exterior features preferably precede, taken in the direction of bit rotation, cutters with which they are associated, and provide sufficient bearing area so as to support the bit against the bottom of the borehole under weight on bit without exceeding the compressive strength of the formation rock.

U.S. Pat. No. 6,363,780 to Rey-Fabret which is herein incorporated by reference for all that it contains, discloses a system and method for generating an alarm relative to effective longitudinal behavior of a drill bit fastened to the end of a tool string driven in rotation in a well by a driving device situated at the surface, using a physical model of the drilling process based on general mechanics equations. The following steps are carried out: the model is reduced so to retain only pertinent modes, at least two values Rf and Rwob are calculated, Rf being a function of the principal oscillation frequency of weight on hook WOH divided by the average instantaneous rotating speed at the surface, Rwob being a function of the standard deviation of the signal of the weight on bit WOB estimated by the reduced longitudinal model from measurement of the signal of the weight on hook WOH, divided by the average weight on bit defined from the weight of the string and the average weight on hook. Any danger from the longitudinal behavior of the drill bit is determined from the values of Rf and Rwob.

U.S. Pat. No. 5,806,611 to Van Den Steen which is herein incorporated by reference for all that it contains, discloses a device for controlling weight on bit of a drilling assembly for drilling a borehole in an earth formation. The device includes a fluid passage for the drilling fluid flowing through the drilling assembly, and control means for controlling the flow resistance of drilling fluid in the passage in a manner that the flow resistance increases when the fluid pressure in the passage decreases and that the flow resistance decreases when the fluid pressure in the passage increases.

U.S. Pat. No. 5,864,058 to Chen which is herein incorporated by reference for all that is contains, discloses a downhole sensor sub in the lower end of a drillstring, such sub having three orthogonally positioned accelerometers for measuring vibration of a drilling component. The lateral acceleration is measured along either the X or Y axis and then analyzed in the frequency domain as to peak frequency and magnitude at such peak frequency. Backward whirling of the drilling component is indicated when the magnitude at the peak frequency exceeds a predetermined value. A low whirling frequency accompanied by a high acceleration magnitude based on empirically established values is associated with destructive vibration of the drilling component. One or more drilling parameters (weight on bit, rotary speed, etc.) is then altered to reduce or eliminate such destructive vibration.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention the method has steps for forming a drill bit with an axis of rotation having a bit body intermediate a shank and a working face. The bit body has a working face with a plurality of blades that may extend outward from the bit body. The working face may comprise at least one cutting element disposed along the blades. A receptacle in the working face of the drill bit may be formed to accept a pocket that is coaxial to the axis of rotation A jack element that is disposed within the pocket and extends from the working face of the drill bit within a range defined by the at least one cutting element proximate the axis of rotation.

In some embodiments the drill bit may be force balanced. The pocket may be brazed and then machined using a mill or lathe to ensure that the jack element is substantially coaxial with the axis of rotation when attached to the pocket. Portions of the at least one cutting element proximate the axis of rotation may be pre-flatted or ground flat in order to accommodate the jack element. The jack element may be brazed, press fit, bonded, welded or threaded into the pocket and protrude from the working face within a range defined by the cutting surface of the at least one cutting element proximate to the axis of rotation Materials suitable for the at least one cutting element or jack element may be selected from the group consisting of diamond, polycrystalline diamond, natural diamond, synthetic diamond, vapor deposited diamond, silicon bonded diamond, cobalt bonded diamond, thermally stable diamond, polycrystalline diamond with a binder concentration of 1 to 40 weight percent, infiltrated diamond, layered diamond, polished diamond, course diamond, fine diamond cubic boron nitride, chromium, titanium, aluminum, matrix, diamond impregnated matrix, diamond impregnated carbide, a cemented metal carbide, tungsten carbide, niobium, or combinations thereof. The jack element may have a distal end with a blunt geometry with a generally hemi-spherical shape, a generally flat shape, a generally conical shape, a generally round shape, a generally asymmetric shape, or combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram of an embodiment of a drill bit assembly with a jack element.

FIG. 2 is a cross sectional diagram of an embodiment of a drill bit assembly with a jack element.

FIG. 3 is a perspective diagram of another embodiment of drill bit assembly depicting a force balanced bit.

FIG. 4 is a cross sectional diagram of another embodiment of a drill bit assembly depicting at least one cutting element that is pre-flattened and a jack element.

FIG. 5 is a perspective diagram of an embodiment of drill bit assembly depicting a method of brazing.

FIG. 6 is a cross sectional diagram of another embodiment of a drill bit assembly depicting a method of machining the pocket using a mill.

FIG. 7 is a cross sectional diagram of another embodiment of a drill bit assembly with a protruding jack element.

FIG. 8 is a cross sectional diagram of another embodiment of a drill bit assembly with a channel.

FIG. 9 is a perspective diagram of an embodiment of a pocket.

FIG. 10 is a diagram of a method for assembling a drill bit with a jack element.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIGS. 1 and 2 disclose a drill bit 100 of the present invention The drill bit 100 is formed to comprise a shank 200 which is adapted for connection to a downhole tool string. A bit body 201 is formed and attached to the shank 200 and comprises an end which forms a working face 202. A receptacle 203 is molded into the working face 202 of the drill bit 100 and may be disposed substantially coaxial with the axis 103 of rotation A pocket 102 which may comprise a material selected from the following including aluminum, titanium, steel, mild steel, hardened steel, stainless steel, a metallic alloy or combinations thereof, may be brazed within the receptacle 203 of the working face 202. In some embodiments the receptacle 203 may not be substantially coaxial with the axis 103 of rotation of the drill bit 100. In other embodiments the working face 202 may form a raised buttress that encapsulates the receptacle 203 and protrudes from the center of the working face 202. A channel 204 may be formed and may extend from the receptacle 203 to a bore 205 within a portion of the bit body 201. The channel 204 may allow air to enter or exit the receptacle 203 when the jack element 101 is inserted or removed and prevent a suction effect. A jack element 101 that may comprise of a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron nitride, and combinations thereof, may be press fit within the pocket 102 such that it may be substantially coaxial with an axis 103 of rotation of the drill bit 100. The working face 202 may also comprise a plurality of blades 104 that are formed to extend outwardly from the bit body 201, each of which may also comprise at least one cutting element 105. Preferably the drill bit 100 will have between three and seven blades 104. In other embodiments the at least one cutting element 105 proximate the axis 103 of rotation of the drill bit 100 may also be pre-flatted or ground flat to accommodate the jack element 101. A plurality of nozzles 106 may also be fitted into recesses 107 formed in the working face 202.

The incorporation of the pocket 102 allows the jack element to be aligned with the axis of the bit. Brazing requires heating, which causes the receptacle to expand and then shrink when cooling. This shrinking may reorient the receptacle such that it is angled or misaligned from the axis. By brazing the pocket of shapeable material, such as steel, into the receptacle and then shaping the pocket such that it is truly aligned with the axis allows the jack element to be press fit into the receptacle such that it is aligned with the axis. It has been found the jack element's life greatly increase the closer it is aligned with the axis of the bit and misalignment caused by shrinking induced during the cooling stage of brazing can greatly reduce the life of the jack element.

Another advantage to press fitting a jack element into the pocket is to avoid brazing the jack element directly. The jack element may be subjected to high loads downhole and in some cases subjecting the jack to the heating and cooling required during brazing may damage the jack element.

FIG. 3 discloses a diagram of an embodiment of a drill bit 100 depicting the placement of the at least one cutting element 105 around the blades 106 so that the drill bit 100 may be force balanced. Vector calculations 300 may be used to calculate the placement the cutting elements 105 around the blades 106 so that the forces acting on the drill bit while engaged in boring through the earth's formations are distributed substantially evenly over the working face of the bit. Specifically the vector calculations 300 may be used to calculate horizontal torque and vertical weight on bit forces acting on the face of each cutting element 105. The calculations may then be used to determine the horizontal components of those forces to determine the net force imbalance. The cutting elements 105 may then be disposed around the blades 106 to help reduce the net force imbalance so that the bit has minimal side force when drilling. Mathematically this is represented by the equations;

SFx=Fx1+Fx2+Fx3+Fx4+Fx5=0

SFy=Fy1+Fy2+Fy3+Fy4+Fy5=0

This embodiment has proven to increase overall durability of drill bits and assists to prolong the life of the cutting elements 105. In other embodiments the vector calculations 300 may also be manipulated to determine optimal positioning of the jack element 101 before being formed in the working face 202 such that the receptacle 203 may be substantially coaxial to the axis 103 of rotation without adversely affecting the balance of the drill bit 100.

FIG. 4 discloses a cross section of an embodiment of the current invention depicting how a portion of the at least one cutting elements 105 proximate the axis 103 of rotation of the drill bit 100 may be machined pre-flat during fabrication or ground flat after fabrication of the working face 202 such that there is sufficient space to accommodate the jack element 101 within the receptacle 203 such that it may be substantially coaxial with the axis 103 of rotation of the drill bit 100. The at least one cutting element 105 may comprise of a polycrystalline diamond compact formed through the HPHT process with a diameter up to 2 inches and a thickness of at least 0.250 inches. In some embodiments, the jack element comprises cubic boron nitride or other ceramic compact to prevent wear.

FIG. 5 discloses a cross section of an embodiment of the present invention wherein the pocket 102 may be brazed into the receptacle 203 of the drill bit 100 using an alloy rod 500 as filler 501 to bond the two elements together. In other embodiments the filler 501 may also comprise of a tape, foil or preform. In other embodiments, the receptacle may be attached through oven brazing. The filler 501 may be selected from the group consisting of copper, silver, nickel, aluminum, gold, tin, zinc, a refractory metal, carbide, tungsten carbide, niobium, titanium, platinum, molybdenum or combinations thereof The embodiment however, may first comprise the steps of cleaning the pocket and/or receptacle using steam, a chemical bath, a degreasing solvent, an abrasive cloth, stainless steel wire brush or combinations thereof, after which flux may be applied to help prevent oxides forming which could weaken the joint during and after heating. The pocket 102 and/or receptacle 203 may then be heated separately to at least 1200° F. before the two are bonded together using the filler 501. The channel 204 may allow air to enter or exit the receptacle 203 when the jack element 101 and/or pocket is inserted or removed and prevent a suction effect. In some embodiments, the channel may also be formed in the pocket, or just in the receptacle.

FIG. 6 discloses a cross section of an embodiment of the pocket 102 which may comprise an annular thickness 600 preferably not less than 0.125 inches and an initial bore with an inner diameter 601 of preferably not less than 0.75 inches. The diagram further discloses an embodiment wherein a portion 602 up to 0.060 inches of the annular thickness 600 may be removed by a mill 603 or lathe (not shown) such that the resultant bore may be realigned to be substantially coaxial with the axis 103 of rotation of the drill bit 100 for receiving the jack element 101.

FIG. 7 discloses a cross section of an embodiment of the jack element 101 that maybe press fit into the pocket 102 such that the jack element protrudes from the working face 202. The jack element 101 may comprise an interference of between 0.0008 and 0.0050 inches. The embodiment also depicts the distal end 700 of the jack element 101 protruding 125% the height 701 of the at least one cutting element 105 proximate the axis 103 of rotation of the drill bit 100 and comprise a domed, rounded, semi-rounded, conical, flat, or pointed geometry. In other embodiments however, the jack element 101 may protrude between 25% and 125% the height 701 of the at least one cutting element 105 proximate the axis 103 of rotation of the drill bit 100. The distal end 700 may further comprise a generally nonplanar interface 702 disposed between a coating of abrasion resistant material 703. The abrasion resistant material may comprise a thickness of between 0.5 and 4 mm. The abrasion resistant material 703 may further comprise a material selected from the following including natural diamond, polycrystalline diamond, boron nitride, tungsten carbide or combinations thereof that may tend to display high wear resistant properties. In a preferred embodiment the abrasion resistant material 703 is sintered to the jack element 101, however the abrasion resistant material 703 may alternatively be brazed, press fit, welded, threaded or otherwise attached to the jack element 101.

FIG. 8 discloses another embodiment of the current invention wherein the channel 204 may be formed to extend from the receptacle 203 into a portion of the nozzle chamber 800. The embodiment also discloses a nonrotating sleeve portion 801.

FIG. 9 is a perspective diagram of an embodiment of a polygonal pocket 1000, which is adapted to receive a polygonal shaped shaft of a jack element. A groove 1001 is formed in the pocket which allows a polygonal shaft to be press fit into the pocket without creating a suction effect. The groove 1001 may run the entire length 1002 of the pocket or just a portion of the length. In other embodiments, the groove 1001 may form a spiral. The polygonal pocket may be closed or open ended on a proximal end 1003 of the pocket. The polygonal pocket 1000 may be brazed, press fit, or otherwise attached into the receptacle of the working face of the bit. While the embodiment of FIG. 9 discloses a polygonal pocket 1000 with an inner and outer diameter 1004, 1005 with generally polygonal shape, in some embodiments, only inner diameter 1004 of the pocket comprises a generally polygonal shape, while in other embodiments only the outer diameter 1005 of the pocket comprises a generally polygonal shape. A polygonal shaft or pocket may be better adapted to resist torque produced during drilling. In some embodiments, a polygonal shaft may require a lesser press fit than a jack element with a more cylindrical shaft. In some embodiments, the pocket may comprise a more permanent attachment to the receptacle than the attachment of the jack element to the pocket, so that it is easier to replace the jack element without having to replace the pocket as well. In some embodiments, the pocket may comprise a thread form on the inner diameter of the pocket for easy installation and removal of the jack element. While the embodiment of FIG. 9 discloses a generally square polygonal shape, the generally polygonal shape may be generally triangular, hexagonal or other polygonal shapes.

FIG. 10 is a diagram of a method 900 of assembling a drill bit 100. The method comprises the steps of forming 901 a drill bit with a body intermediate a shank and a working portion comprising at least one cutting element and a receptacle in the working face with a channel from the receptacle to a bore of the bit body; grinding 902 the at least one cutting element proximate the axis of rotation to accommodate the jack element; brazing 903 a pocket within the receptacle; machining 904 the pocket within the receptacle such that its bore is substantially coaxial to the rotation of the drill bit; press fitting a jack element within the pocket such that the jack element protrudes from the working face.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention. 

1. A method of assembling a drill bit with a substantially centered jack element comprising; providing a drill bit with a bit body intermediate a shank and a working face comprising at least one cutting element; forming a receptacle in the working face co-axial within an axis of rotation of the drill bit for reception of a pocket; attaching the pocket within the receptacle; securing the jack element within a portion of the pocket such that the jack element may be substantially coaxial with the axis of rotation
 2. The method of claim 1, wherein the method further includes a step of forming a channel from the receptacle to the bore of the bit body.
 3. The method of claim L wherein an inner diameter of the pocket comprises a groove.
 4. The method of claim 1, wherein the drill bit is force balanced such that the receptacle is substantially coaxial with the axis of rotation before machining to accept the pocket.
 5. The method of claim 1, wherein the at least cutting element proximate the axis of rotation is pre-flatted to accommodate the jack element.
 6. The method of claim 1, wherein the method further comprises the step of grinding a portion of the at least one cutting element proximate the axis of rotation to accommodate the jack element.
 7. The method of claim 1, wherein the pocket comprises a material selected from aluminum, titanium, steel, mild steel, hardened steel, stainless steel, a metallic alloy or combinations thereof.
 8. The method of claim 1, wherein the pocket comprises an annular thickness not less than 0.125 inches.
 9. The method of claim 1, wherein the pocket comprises an inner diameter not less than 0.75 inches.
 10. The method of claim 1, wherein the pocket is brazed within the receptacle.
 11. The method of claim 11, wherein the step of brazing the pocket within the receptacle comprises a brazing alloy filler selected from the group consisting of copper, silver, nickel, aluminum, gold, tin, zinc, a refractory metal, carbide, tungsten carbide, niobium, titanium, platinum, molybdenum or combinations thereof
 12. The method of claim 11, wherein the brazing alloy filler may comprise of a tape, foil, or preform
 13. The method of claim 1, wherein the is machined such that it is substantially coaxial to the axis of rotation to accept the jack element using a mill or lathe.
 14. The method of claim 1, wherein the jack element comprises a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron nitride, and combinations thereof.
 15. The method of claim 1, wherein at least a portion of the jack element is press fit into the pocket.
 16. The method of claim 1, wherein the step of press fitting the jack element within a portion of the pocket comprises an interference of between 0.0020 and 0.0025 inches.
 17. The method of claim 1, wherein the jack element may protrude from the working face of the drill bit between 25% and 125% of the height of the at least cutting element proximate the axis of rotation
 18. The method of claim 1, wherein the jack element may comprise a coating of abrasive material comprised of a material selected from the following including natural diamond, polycrystalline diamond, boron nitride, tungsten carbide or combinations thereof
 19. The method of claim 14, wherein the coating of abrasion resistant material comprises a thickness of 0.5 to 4 mm.
 20. The method of claim 1, wherein the jack element comprises a distal end comprising a domed, rounded, semi-rounded, conical, flat, or pointed geometry.
 21. The method of claim 1, wherein the at least one cutting element comprises a polycrystalline diamond compact with a thickness at least 0.250 inches.
 22. The method of claim 1, wherein the jack element comprises a polygonal shaft. 